Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $195.85   8.260%   $212.0272   $212.03   $212.05   $212.00  
  Purchase #2 $172.92   8.493%   $187.6061   $187.61   $187.60   $187.60  
  Purchase #3 $27.29   4.793%   $28.598   $28.60   $28.60   $28.60  
  Purchase #4 $142.93   8.871%   $155.6093   $155.61   $155.60   $155.60  
  Purchase #5 $5.30   8.527%   $5.7519   $5.75   $5.75   $5.80  
  Purchase #6 $56.30   13.151%   $63.704   $63.70   $63.70   $63.70  
  Purchase #7 $103.45   5.839%   $109.4904   $109.49   $109.50   $109.50  
  7 purchase totals = $704.04       $762.7869   $762.79   $762.80   $762.80